The present invention relates to a continuous photosensitive web having a leader portion and further relates to a light-shielding packaging for a roll of the photosensitive web.
A light-shielding packaging for a roll of continuous photosensitive web wound on a core having on its each end a light-shielding flange disc is known and actually utilized, particularly, for the purpose of roomlight loading of a roll of continuous photosensitive web into a camera or other image-forming apparatus in which the photosensitive web is to be exposed.
European Patent Application No. 0 181 417 A1 (issued on May 21, 1986) discloses a packaging of rolls of light-sensitive material such as strip of photographic film or paper, for roomlight loading. The packaging comprises opaque material which protects the rolled material from light while leaving a leader of the rolled material exposed and which can be torn by pulling on such leader to cause the light-sensitive material to commence unwinding from the roll. A piece of heat-shrinkable sheet material is used together to cover the leader as well as a portion of the light-sensitive material.
U.S. Pat. No. 4,733,777 (issued on Mar. 29, 1988) and European Patent Specification 0 230 057 B1 (issued on May 16, 1990) both disclose a light-tightly packaged roll of light-sensitive material, which comprises an annular end cover for each end face of the roll and a circumferential cover wound around the periphery of the roll and having lateral extensions sealed with their inner surface to the inner surface of radially outwardly projecting margins of the end covers.
U.S. Pat. No. 4,911,299 (issued on Mar. 27, 1990) discloses a strip of light sensitive material wound in a coil onto an open-ended core which is packaged in tearable light tight wrapping material protecting the rolled web while leaving an exterior end of the coil exteriorly accessible. The light tight wrapping material is tearable by pulling on the exterior end to commence unwinding of the coil from the core.
European Patent Application 0 681 212 A1 (issued on Nov. 8, 1995) and U.S. Pat. No. 5,472,089 (issued on Dec. 5, 1995) both disclose a light-tight packaging for photosensitive web roll having a flexible leader portion that overlaps the outermost first convolution of the roll. The leader has three stretchable segments in which can cooperate with light-shielding flange portions to form light-tight labyrinth-type sealing.
Thus, for the purpose of satisfactory light-tight sealing, known packagings for photosensitive web utilize overall light-shielding sealing which is tearable when the leader is pulled to commence unwinding of the photosensitive web, or structural sealing such as labyrinth-type sealing.
The present invention has an object to provide a new light-shielding packaging system for a roll of continuous photosensitive web wound on a core having on its both ends a light-shielding flange disc.
The invention further has an object to provide a continuous photosensitive web having a light-shielding leader sheet, which is favorably employable for the new light-shielding packaging system.
The invention furthermore has an object to provide a continuous photosensitive web having a light-shielding leader which shows a high dimensional stability at surrounding temperatures which the photosensitive web sometimes encounters.
The invention resides in a continuous photosensitive web having at least at its one end a heat-shrinkable light-shielding leader sheet having a thickness of 30 to 200 xcexcm, preferably 70 to 150 xcexcm, more preferably 80 to 130 xcexcm, and comprising a resin material and a colorant which shows a heat shrinkage ratio at 50xc2x0 C. of lower than 1%, preferably lower than 0.5%, both in the longitudinal and width directions of the web and a heat shrinkage ratio at 100xc2x0 C. in the range of 5% to 30%, preferably 10 to 30%, more preferably 15 to 30%, in the longitudinal direction and a heat shrinkage ratio at 100xc2x0 C. of less than the heat shrinkage ratio in the longitudinal direction by 1% or more, preferably 3% or more, more preferably 5% or more, in the width direction.
The invention further resides in a light-shielding packaging for a roll of continuous photosensitive web wound on a core having on its each ends a light-shielding flange disc, which has at its leading end a heat-shrinkable light-shielding leader sheet having a thickness of 30 to 200 xcexcm, preferably 70 to 150 xcexcm, more preferably 80 to 130 xcexcm, and comprising a resin material and a colorant which shows a heat shrinkage ratio at 50xc2x0 C. of lower than 1%, preferably lower than 0.5%, both in the longitudinal and width directions of the web and a heat shrinkage ratio at 100xc2x0 C. in the range of 5% to 30%, preferably 10 to 30%, more preferably 15 to 30%, in the longitudinal direction and a heat shrinkage ratio at 100xc2x0 C. of less than the heat shrinkage ratio in the longitudinal direction by 1% or more, preferably 3% or more, more preferably 5% or more, in the width direction, said leader sheet having a length larger than the length of the outermost convolution of the roll and a width larger than the distance between the outer face of one flange disc and the outer face of another flange disc, and each side portion of the leader sheet being light-tightly attached via heat shrinkage thereof to the outer face of the flange disc at least at a portion adjacent to the periphery of the flange disc.
The heat shrinkage ratio can be determined under the conditions defined in JIS Z 1709-1976. The heat shrinkage ratio at 50xc2x0 C. is measured in water heated to 50xc2x0 C., while the heat shrinkage ratio at 100xc2x0 C. is measured in silicone oil heated to 100xc2x0 C.
A ratio of the heat shrinkage ratio of the leader sheet in the longitudinal direction to the heat shrinkage ratio in the width direction is preferably 3 or more, more preferably 4 or more, most preferably 5 or more.